Tell your boss, who clearly doesn't know WTF is going on. If you've got an HR department, then tell them, too.
Also, I can't figure out what MD is in the context of your post. Is he asking you if you do drugs, or something?
Tell your boss about the unwelcome touching and this guy dissing elderly people first, as those may be enough. If they aren't, then also mention the inappropriate comments about appearance, and that he seems to be trying to ask one of your coworkers out or at least for something social after hours which is not welcome.
Only mention his muttering to himself as a last resort.
Tell your boss that you also think this guy would retaliate with violence if he found out you were saying anything and demand full cooperation when it comes to your boss never mentioning to this guy that anyone in particular complained.
In fact, it may do better if you didn't do this alone. Can any of your coworkers support this and even offer anecdotes of their own? Particularly the women he's pushing to give him a tour.
Several years ago I worked in a law firm where the clerical staff got a new boss who they all hated. One by one, the secretaries started quitting. The managing partner had become social friends with the clerical boss so he wasn't seeing the problem until finally an African-American secretary quit and specifically told him just how racist the clerical boss really was. Then the clerical boss was shown the door. But that wasn't until something like 6 people had left.
It's expensive to hire and train new staff. It's all mentally and physically draining. But your boss may very well respond to making it clear to him that he can either keep this guy and risk a half a dozen of you walking out, or letting this guy go and keeping the rest of you, and only have to hire one person.